Field of the Invention
The present invention relates to a secondary battery abnormality notification system for notifying that an abnormality has occurred, based on leakage of active material from at least a secondary battery.
Description of the Related Art
In general, frequency adjustment in an electric power system and adjustment of power demand and power supply in the electric power system are carried out using a plurality of power generators, storage batteries, etc., equipped in the electric power system. Further, in most cases, adjustment in difference between electric power generated by natural energy power generators and the planned output electric power, and reduction in change of electric power generated by the natural energy power generators are also performed using the power generators, storage batteries, etc. In comparison with general electric power generators, the storage batteries can change the electric power output at high speed, and thus is effective in frequency adjustment of the electric power system, adjustment of the difference between the generated electric power from the natural energy power generators and the planned output electric power, and adjustment of power demand and power supply in the electric power system.
In this regard, as a high-temperature operation type storage battery connected to the electric power system, a sodium-sulfur battery (hereinafter referred to as the NaS battery) is used, for example. This NaS battery is a high temperature type secondary battery containing metal sodium and sulfur as active materials in an isolated manner using a solid electrolyte pipe. When the NaS battery is heated at high temperature of about 300° C., a certain amount of energy is produced by an electrochemical reaction of both of the melted active materials of these metal sodium and sulfur. Normally, the NaS battery is foisted by assembling a plurality of battery cells, and used in a form of a module including a plurality of battery cells connected together. That is, the module has a structure where circuits (strings) each formed by connecting a plurality of battery cells in series are connected in parallel to form a block, and at least two blocks are connected in series, and placed in a heat insulating container.
As a method of reporting occurrence of an abnormality of such a module, a method of detecting an abnormality of a battery by comparing electric discharge depth of each block, and reporting the abnormality has been disclosed (e.g., Japanese Laid-Open Patent Publication No. 03-158781). In this method, the presence or absence of the abnormality is determined for each of the blocks of the module. Therefore, in comparison with the case of detecting the abnormality for each of the NaS battery cells of each block, the apparatus is not complicated, and the production cost can be reduced advantageously.